Asymmetric contribution of α and β subunits to the activation of αβ heteromeric glycine receptors

• Published in: Journal of neurochemistry Vol. 86; no. 2; pp. 498 - 507
• Main Authors: Shan, Qiang, Nevin, Simon T., Haddrill, Justine L., Lynch, Joseph W.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.07.2003; Blackwell
• Subjects: allosteric interactions; Aminoacid receptors (glycine, glutamate, gaba); Biological and medical sciences; Cell receptors; Cell structures and functions; Fundamental and applied biological sciences. Psychology; gating; glycine receptor chloride channel; Molecular and cellular biology; receptor structure and function; substituted cysteine accessibility method; Interaction; substituted cysteine accessibility method; Activation; Ionic channel; Ionic current; Gene expression; Glycine; Subunit; allosteric interactions; Sensitivity; Cell line; glycine receptor chloride channel; Chlorides; Glycine receptor; receptor structure and function; Mutation; Gating
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1046/j.1471-4159.2003.01872.x

This study investigated the role of β subunits in the activation of αβ heteromeric glycine receptor (GlyR) chloride channels recombinantly expressed in HEK293 cells. The approach involved incorporating mutations into corresponding positions in α and β subunits and comparing their effects on receptor function. Although cysteine‐substitution mutations to residues in the N‐terminal half of the α subunit M2–M3 loop dramatically impaired the gating efficacy, the same mutations exerted little effect when incorporated into corresponding positions of the β subunit. Furthermore, although the α subunit M2–M3 loop cysteines were modified by a cysteine‐specific reagent, the corresponding β subunit cysteines showed no evidence of reactivity. These observations suggest structural or functional differences between α and β subunit M2–M3 loops. In addition, a threonine→leucine mutation at the 9′ position in the β subunit M2 pore‐lining domain dramatically increased the glycine sensitivity. By analogy with the effects of the same mutation in other ligand‐gated ion channels, it was concluded that the mutation affected the GlyR activation mechanism. This supports the idea that the GlyR β subunit is involved in receptor gating. In conclusion, this study demonstrates that β subunits contribute to the activation of the GlyR, but that their involvement in this process is significantly different to that of the α subunit.